Although standard techniques are available, intra-laboratory variation in the quality and number of bone cells available for research purposes at Yale has varied considerably. To address this limitation and to advance productive scholarship, the Yale Core Center for Musculoskeletal Disorders developed the Cell Core. The mission of the Cell Core is to facilitate the experimental use of authentic, primary, mouse and rat osteoblastic cells as well as osteoclasts generated from in vitro culture. As part of our new initiatives bone marrow derived mesenchymal stem cells (MSCs) are now available to Core investigators. Although outside the original mandate of the Core, the Director has made his PIXImus machine available to Center members through an agreement with the Densitometry subunit of the Physiology Core. The Specific Aims of the current proposal are to provide the following services: 1. Isolate and cultivate primary murine and fetal rat calvarial osteoblasts. This will include large-scale preparations for biochemical studies and RNA and DNA purification. 2. Cultivate murine osteoclast-like cells generated from: 1) in vitro co-culture 2) culture with M-CSF and RANKL. 3. Maintain a wide range of frozen cell lines. 4. Provide small animal bone densitometry (DEXA). 5. Cultivate mouse bone marrow derived mesenchymal stem cells (MSCs). 6. Train for in vitro isolation and culture of osteoblasts, osteoclasts and stromal cells, so that investigators, appropriately trained, can initiate and maintain these cells in their laboratories. The Cell Core is particularly anxious to support current and future Pilot and Feasibility Projects as part of the Center's ongoing effort to attract new investigators to musculoskeletal research.